feat: simplify parens

src/alejandra_engine/src/builder.rs

@@ -191,7 +191,7 @@ fn format(
                 rnix::SyntaxKind::NODE_INHERIT => crate::rules::inherit::rule,
                 // ( a )
                 rnix::SyntaxKind::NODE_INHERIT_FROM => {
-                    crate::rules::paren::rule
+                    crate::rules::inherit_from::rule
                 }
                 rnix::SyntaxKind::NODE_KEY => crate::rules::default,
                 // a = b;

src/alejandra_engine/src/rules/inherit_from.rs

@@ -0,0 +1,6 @@
+pub(crate) fn rule(
+    build_ctx: &crate::builder::BuildCtx,
+    node: &rnix::SyntaxNode,
+) -> std::collections::LinkedList<crate::builder::Step> {
+    crate::rules::paren::rule_with_configuration(build_ctx, node, false)
+}

src/alejandra_engine/src/rules/mod.rs

@@ -4,6 +4,7 @@ pub(crate) mod bin_op;
 pub(crate) mod dynamic;
 pub(crate) mod if_else;
 pub(crate) mod inherit;
+pub(crate) mod inherit_from;
 pub(crate) mod key_value;
 pub(crate) mod lambda;
 pub(crate) mod let_in;

src/alejandra_engine/src/rules/paren.rs

@@ -1,6 +1,14 @@
 pub(crate) fn rule(
     build_ctx: &crate::builder::BuildCtx,
     node: &rnix::SyntaxNode,
+) -> std::collections::LinkedList<crate::builder::Step> {
+    rule_with_configuration(build_ctx, node, true)
+}
+
+pub(crate) fn rule_with_configuration(
+    build_ctx: &crate::builder::BuildCtx,
+    node: &rnix::SyntaxNode,
+    simplify: bool,
 ) -> std::collections::LinkedList<crate::builder::Step> {
     let mut steps = std::collections::LinkedList::new();
 
@@ -10,6 +18,29 @@ pub(crate) fn rule(
     let expression = children.next().unwrap();
     let closer = children.next().unwrap();
 
+    // Simplify this expression
+    if simplify
+        && !opener.has_inline_comment
+        && !opener.has_comments
+        && !expression.has_inline_comment
+        && !expression.has_comments
+        && !closer.has_inline_comment
+        && !closer.has_comments
+        && matches!(
+            expression.element.kind(),
+            rnix::SyntaxKind::NODE_ATTR_SET
+                | rnix::SyntaxKind::NODE_IDENT
+                | rnix::SyntaxKind::NODE_LIST
+                | rnix::SyntaxKind::NODE_LITERAL
+                | rnix::SyntaxKind::NODE_PAREN
+                | rnix::SyntaxKind::NODE_PATH_WITH_INTERPOL
+                | rnix::SyntaxKind::NODE_STRING
+        )
+    {
+        steps.push_back(crate::builder::Step::Format(expression.element));
+        return steps;
+    }
+
     let vertical = opener.has_inline_comment
         || opener.has_trivialities
         || expression.has_inline_comment

src/alejandra_engine/tests/cases/paren/out

@@ -2,19 +2,19 @@
   ( # test
     a # test
   )
-  ((c))
+  c
   (
-    (c)
+    c
     /*
      e
      */
   )
-  ((
+  (
     c
     /*
      d
      */
-  ))
+  )
   (
     (
       c
@@ -26,12 +26,12 @@
      e
      */
   )
-  ((
+  (
     /*
      b
      */
     c
-  ))
+  )
   (
     (
       /*
@@ -43,15 +43,15 @@
      e
      */
   )
-  ((
+  (
     /*
      b
      */
     c
     /*
      d
      */
-  ))
+  )
   (
     (
       /*
@@ -70,13 +70,13 @@
     /*
      a
      */
-    (c)
+    c
   )
   (
     /*
      a
      */
-    (c)
+    c
     /*
      e
      */

src/alejandra_engine/tests/cases/with/out

@@ -61,11 +61,9 @@
   }
   {
     binPath = with pkgs;
-      makeBinPath (
-        [
-          rsync
-          util-linux
-        ]
-      );
+      makeBinPath [
+        rsync
+        util-linux
+      ];
   }
 ]